rc4me center diff Super 5SC transmission in my HPI Savage Flux HP

olds97_lss

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I got some thicker o-rings from China on ebay to put in the cups. That seems to have stopped my binding/chatter issues in the front.

However, I also bought an Arrma outcast... you know what happens when you get a new truck, you drive it... A LOT! Haven't had my savage off the shelf in a couple weeks. Been off work all this week just to take a break and have been running my outcast all week. Being able to air a truck out without having to worry about shocks is quite a blast! However, I think I may have a new problem. To gear it similar to my savage, the esc/motor runs hot on 4S. I may have to change to 6S... good thing I just bought 4 more 2S packs a couple months ago...
 

olds97_lss

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Looks like that one comes with grease all over in it. Mine was pretty dry inside. Actually worked out well since the first thing I did was have to take it apart to put oil in the center diff. Less of a mess to work on.

Also has the input shaft without a hex on it for the slipper spring washer. That was something I transferred over from my stock flux transmission or odds are it would have tightened/loosened itself with use. Odd that HPI did that.

 

orzowei69

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Hi olds97_lss,
did you fill your center diff completely with oil?
I am using 1M oil in It. If I fill It completely It will hardly move. I had to leave a bit of air inside (about 1/6 of space) so that the oil could flow when the inside gears move.
If I fill It completely, resistance to movement is greatly affected by the pressure of the oil against the diff housing when trying to flow.
Originally the diff had grease inside and was not completely filled.
To fill completely or not to fill completely that is the question.
 

olds97_lss

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I filled it up to the top of the X bars like normal. 2/3 500K and 1/3 1M associated oil. I let it sit overnight with the sun gear that goes on the ring gear resting on the blob of 1M I added and by morning the oil had fully settled. When I put the ring gear on and tightened it down, the oil didn't ooze out anywhere.
 

olds97_lss

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I'm currently running 6S with this and it's going ok. I had to gear down quite a bit as my motor/esc aren't handling it too well. I believe I'm at 48/16 now. The esc still runs warm even with an upgraded fan that is wired to always be on and I mounted a fan next to the motor. The last time I ran it, it didn't thermal on me and I ran it pretty hard for 20 minutes straight, which is how long the Hobbystar 6200mah packs lasted. I also installed a 6x1800uf cap pack I made, which greatly helped the ripple voltage in my esc log. I'm running the castle MMX/2200kv sensored setup. I may look for a lower kv motor to see if that helps lessen the load on the esc.

Footage/discussion from my last run:
https://www.hpisavageforum.com/thre...with-a-cap-pack-at-the-grass-bmx-track.19445/

Discussion regarding gearing for 6S:
https://www.hpisavageforum.com/threads/savage-flux-hp-gearing-for-6s.19348/

Footage discussion from when I had 47/16:
https://www.hpisavageforum.com/thre...-08-savage-flux-6s-and-stampede-4x4-3s.19385/

The gear mesh wasn't that great and it overheated on me which is why tried a 48T. I'm not sure if I can step down to 48/15 and still have good mesh. Might try that before I take it out again.
 

olds97_lss

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Now you don't need the hex key on that input shaft.;)
View attachment 7076
Yeah, I kind of like the slipper though. Takes out some of the shock when all 4 tires land hard. That makes for a simple install though. Do you have them in other sizes? I'm running a 48T at the moment since I'm running 6S. May even go a bit lower to lower my temps more... or change to a lower kv motor.
 

Savage 6768

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New Zealand
I am thinking of trying this center diff set up, I already have a center diff cup with the spider gears but will need the rest of the parts to complete it. My question is does anyone have the part numbers to make up the center diff ? Forgot to mention I have the flux hp gear box Cheers
 
Last edited:

Savage 6768

Active Member
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New Zealand
Just been looking at the parts list for the 5sc diff. If I am correct I would need the following to complete
#106273 diff cup holder
#CD 30T gear
Only problem I can not find #106279 which is the output shafts ( which are straight shafts) from the center diff. I wondering if I could use the normal diff outputs that the dog bones go into like on a center diff say in a 1/8 buggy/ truggy . Hope this makes sense
 

olds97_lss

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Updated first post with new image hosting:
Well, I got the rc4me center diff trans. On my bench, I'm not sure how other guys have installed it. A few things differ that I need to deal with before moving forward with it. I got it for the sole purpose of trying to help my diffs last longer. Even running 4S, I still have busted 3 or 4 diffs on bad rear or front end landings. Hopefully this will help in those situations.

The first issue, the input shaft isn't keyed to the hex washer like the stock input shaft. So, if the slipper slips, an unkey'd washer is going to be likely to spin with the spur and not the shaft which will be prone to cause the slipper to adjust itself on the fly if/when it slips. I used the original flux shaft in it's place.



The second, the gear ratio is different. I'm not smart enough to figure out which way it's different, just that it's different.

The stock flux hp trans I have has the following:
2 gear input, 18/23. The smaller of the two being used. 18 -> 44, the 44 is on the same shaft as the next gear, 33 which spins the output 29.

RC4Me trans:
1 gear input, 21. Spins gear 41 which is on the same shaft as the next gear, 31, which spins the output gear/diff 30.

I'm not sure if this math is right:
stock
18-44 32-29

18/44=.409
32/29=1.103
.409*1.103= .45

rc4me
21-41 31-30
21/41=.512
31/30=1.033
.512*1.033= .53

If that's the case... I'm not sure which is higher geared and by how much so I know what pinion I might want to use to be close to what I have now. I suck at this stuff. If anyone could help, I'd appreciate it. I changed my pinion from a 21T to a 20T just to be safe since I had one on hand. I was intending on changing it anyway since the ESC does run a bit warm as I had the 21T in there when I had tires smaller than the trenchers and never changed the pinion back. In doing so, I'm not sure I can make the pinion any smaller to deal with the new gear ratio if I have to. If I do, I may not be able to tighten the outside screws on the motor plate as the TVP will be in the way. Suppose I could dremel grooves in it...

Here are the RC4ME gears with tooth counts for anyone wondering:




The center diff was missing a shim in the gear side of the diff. The thing uses a weird bearing combination on the cup side. It has one bearing on the cup like a normal diff and another bearing on the shaft itself that goes on from outside the trans case vs inside. The front dog bone cup keeps it in place. The bearing on the gear side of the cup towards the rear of the truck was metal shielded. I replaced it with a rubber shielded one.

The diff cup "cap" in case anyone wanted to see it:



The inside of the diff was nearly dry with only a little bit of grease. Probably makes sense since most people would clean it out and put silicone oil in it anyway.


It didn't have locktite on any of the screws either. One of the output shafts is longer than the other. I didn't realize that until I had already take it apart and cleaned off the grease. I think the longer one goes on the front cup side... now I can't recall.

I used associated 500k in the diff before dropping the spider gears in. I put enough in so that it was nearly to the top of the x bars once they were installed and seated. I put a blob of 200k on top as I wasn't sure which way to go, so figured once the oil mixes, I'll be less than 500 and more than 200. lol

The final issue was when I installed the rear output shaft cup, the plastic grub screw retainer and a hair of the cup rubs slightly on the trans case. I dremeled a bevel in the retainer for a bit more clearance. It's barely rubbing. Guessing after a few minutes of driving, it will remove a bit of material and not rub anymore.

Will post up how it does hopefully tomorrow. It's supposed to be mid-90's here with high humidity... not sure I want to go outside, but I really want to see how this thing does.
 

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